Which paper did you use? I used a glossy paper and Gabor still seems to see some structure in my images. I could try to use the same paper as you did.

Best regardsErik

ErikInk Jet Art Micro Ceramic LusterI would have used their Duo Bright Matt (less texture) but I was outThe luster had a few reflections so I carefully positioned 2 daylight fluorescents one on each sideMarc

[attachment=11601:Marc_LL_...lections.GIF]The shots of the color checker provided by Marc are excellent for measurement. The attached graphs confirm, that the result is reliable; the values from the three raw channels are picked from all 24 patches of the color checker without contradiction (no manual adjustment took place).

What one can see from the graphs directly is:

1. ISO 50 and 100 are virtually identical, as they are supposed to be,

2. ISO 3200 is exactly 1 EV from ISO 1600. This is important, for ISO 3200 is not a fake ISO, nevertheless it should not be used when shooting raw, for it reduces the DR by a full stop,

3. the increasing spacing of the graphs with increasing ISO demonstrates, that the higher the ISO step, the less the real gain from the previous step (i.e. the more loss of the DR).

I am not a big fan of these graphs, I find them pretty useless. I will put the numbers in Excel charts with other cameras' data. I have now reliable measurements from the Canon 10D, 20D, 40D, 50D, 1DMkII, 1DMkII and Nikon D3, and Erik will provide the shots with a Sony A900.

UPDATE

Somehow I messed up the attachments; the formerly displayed graphs were from the Canon 50D. Sorry for that.

If one plots (noise)^2 vs signal, the inverse of the slope is the gain in electrons/raw level, and the intercept at zero signal is the read noise squared. The other thing that is useful to plot is log(S/N) vs log(S), which provides a more complete picture of image quality over the dynamic range of a capture.

All I can say is that this is a measure of the combined effects of sensor performance, pre-amplification, tone curves, noise reduction etc.

Once a camera has options for dealing with contrasty scenes (ones of high subject brightness range) it is rather pointless to attach any value to high DR measurements from default JPEG settings. The default settings of all cameras are providing completely adequate DR for normal scenes, and are not usually intended to be used with highly contrasty scenes. Indeed, JPEG's that score well for DR will probably give a flatter look to typical scenes, due to using a flatter tone curve.

The options for dealing with high SBR scenes do not need to be just "shoot RAW and fix it in post"; they can be things like Nikon's D-lighting, or as simple as lower contrast settings.

According to DPreview, the Canon 5D MKII can capture the same DR from ISO100 to ISO1600. But that is not all folks, it can even capture more DR at ISO3200!

Yes, too bad the 5DII DR is at best equal to, but in most cases less than, the DR of the D3X over the same range. This is according to DPReview, so the same measuring methodology was used in both cases. In fact, at ISO 3200, the D3X DR is 9.3 stops.

I filled the spreadsheet with reliable data (i.e. measured on Stouffer transmission wedge or on the even better printed color chart) from Nikon D3, Canon 20D, 40D, 50D and 5DMkII. The Canon 1DMkII and 1DMkIII are coming.

It is downloadable as an Excel chart; however, I am not happy with that. It does contain all the measurement data, but it is not easy to use. It can be sorted, of course, but that's not enough for me.

The data beside the camera model and ISO is the relative intensity of the measured points, in EV from clipping backwards, and the correlated noise in percentage of the average pixel intensity.

Example: the Canon 5DMkII with ISO 100 has 21.6% noise when the intensity is -8.9 EV (i.e. close to the end of the 9th stop of the dynamic range).

Now, if you want to compare this with the D3, then look for a row among the ISO 100 rows, containing the closest value to 8.9 (this is at the moment 8.92); the correlated noise is 17%. In turn, if you want to know the difference in EV, then look for a row with close to 21.6%; I interpolate this to -9.25 EV, i.e. the D3 has 0.35 EV advantage at ISO 100 (the accuracy of the measurements does not justify to talk about hundredths of an EV).

I would like to make a better presentation, but I don't want to invest too much work in that; anyway, at the moment I am still collecting data (measuring other cameras' results).

Assuming that the mapping of incident photon count and value recorded is linear and constant, this isn't possible; the noise is what determines dynamic range.

Sorry, I missed that comment. This surprisingly similar DR at different ISOs results from in-camera processing of the raw data. Noise is only one factor in determining DR. You can reduce the DR of any image by simply applying a tone curve that brightens the highlights and darkens the shadows. This is usually what tends to happen with in-camera jpegs. The images are processed to look 'punchy' and there's a consequent loss of detail in the brightest highlights and the darkest shadows..

There are a couple of comments from Dpreview in the comparison between the 5D2 and D700, which give an indication as to what might be going on here. There's apparently a quite significant loss of resolution in 5D2 images at ISO 3200 which brings resolution down to the level of the D700 at ISO 3200. One might conclude that this is a result of excessive in-camera noise reduction being applied to the 5D2 image, more than is being applied to the D700. However, Dpreview also note that D700 RAW images are also a whisker more detailed than 5D2 RAW images at ISO 3200.

This tends to suggest that the reason for the high DR of 5D2 in-camera jpegs at ISO 3200 is not excessive noise reduction, but a flatter or less contrasty (or simply different) tone curve which preserves all the DR that is present in the RAW data. Such a view tends also to be confirmed by Dpreview's comparison of RAW DR with jpeg DR at ISO 3200. Jpeg DR at ISO 3200 is almost 2 stops down from the best ACR conversion at base ISO. DXOmark similarly claim that the 5D2's sensor at ISO 3200 has 2 stops less DR than at base ISO.

One might therefore draw the conclusion that Cannon have simply done a first rate job with in-camera processing of ISO 3200 RAW data, preserving all the DR that exists. However, at base ISO, and other ISOs in between, they have made a decision to sacrifice a certain amount of DR in the interests of a better looking result straight out of the box.

Those who already own a 5D2 should be able to confirm this hypothesis by comparing RAW conversions of ISO 3200 images with in-camera jpegs of the same scene taken at ISO 3200. Can you extract any more DR than the in-camera processing does, from the RAW image at ISO 3200?

It is downloadable as an Excel chart; however, I am not happy with that. It does contain all the measurement data, but it is not easy to use. It can be sorted, of course, but that's not enough for me.

That's excellent stuff Gabor, pity you didn't produce data for the upper f-stops. I think they can also be interesting in terms of noise, for example if the user plans to systematically do exposure bracketing to work only in the cleanest ranges of the sensor (like I do).

I took the freedom to plot your 5D MKII data in the form of SNR plots in dB:

Conclusions:

Per-pixel DR of this camera with SNR>12dB criteria would be around:9.1EV at ISO1009.0EV at ISO2008.7EV at ISO4008.2EV at ISO8007.5EV at ISO16006.5EV at ISO3200

It's easy to see on them that ISO50 is a true ISO100 as you found out.

I also plotted the SNR improvement curve obtained by rising ISO, and as Emil predicted according to his measures and I have analysed in some RAW files from this camera, there is no improvement in reaching ISO3200 even if it's an electronic ISO value (DR at ISO3200 is exacly 1EV less than at ISO1600).

Just for checking I compared the value for ISO1600 at -6EV, which provides SNR=17dB -> SNR=2,8EV which agrees with Emil's plot here for the similar sensor 1Ds MKIII.

Find the Excel file here. I plotted the graphs one by one and layered them in PS.

The same graph from the 50D data:

Per-pixel DR of this camera with SNR>12dB criteria would be around:8.7EV at ISO1008.7EV at ISO2008.25EV at ISO4007.5EV at ISO8006.7EV at ISO1600